HoboJen - How tall are you? I read these threads about build ideas and am amazed that no one asks that question.
Why? Because if gyou are about 5' 10" you can sleep across a Ford van and have tons of room and layout oprtions that you cannot if you are 6' or taller.
We have a Ford E350 EB 15 Pass XLT w/ Rear A/c and heater!! Sleeping bed with 4" of foam is side to side across the back and designed to be for two but can be reduced in width to one . Elevation puts the the top of the foam just above window sills. Clearance under the bed platform is 18" clear and 4 ft wide, storage space on sides is still accessible. This allows six plastic bins worth of gear, food, or water tank, etc under the bed and two to three bins accessible inside. Never have to convert the bed for anything which is really nice. Behind drivers seat is Norcold mrft60 refrig/freezer and in our case, one of the stock bench seats running under the side windows serves as lounge. This could easily could be the sink/ counter/fridge, etc. Passenger swivel base is mandatory, imho. Put pop out windows in rear and screen all the other windows. Black out panels for privacy. Vent shades on front windows with velcro attached screens and you have lots of ventilation. No pop top really needed. How often are you inside and needing onstand up. Cooking inside? Almost no one uses a stove inside. Use the microwave or a small single burner camp stove if really needed.
Opposite side can be microwave, cabinets, door mounted galley, etc. Our toilet is a bucket with some water with lid because in the middle of night one sometimes needs to go. Shower is sponge bath with nice warm water. Shower is campground, 24 hr fitness mebership, or some other solution. Heat is via Wave 3. Easily stored, super efficient ( leave window cracked and wipe down moisture in morning if an issue). House batteries mount on frame and there is room for three to four. Inverter gets you powered.
We have the V10, very reliable, powerful, etc. Added 46 gal Transferflow Gas tank and Quadvan 4x4. Mileage is 13.5 mpg. With my tank, my driving range is 500 plus. Get a V8, no 4x4 and you are looking in the 16mpg plus.
Roof rack - get four Thule bars with 387 towers. You can add boxes, racks, kayak mounts, whatever. Use a telescopic ladder to get up there and store it away easily when not needed. Solar needed- go portable as one would likely want to park the van in the shade. Tow hitch for bike mount, toad, additional storage.
Add food, water and you are ready to go. Set up a good unit and your resale is there. Take this advice from someone older - get out there soon before life catches up with you. Time definitely flys by as we get older. Ten years will pass so fast you will not even believe it. Hard to see on your side of ten years but easily seen on the back side of it. Get going, the formula is above and many here have provided great advice. My suggestion is a Ford E250/350 extended window with XLT. Lots of late model around at really good prices.
Peace!!!